Nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, lithium secondary batteries, etc. are currently commercialized, and the lithium secondary batteries among those batteries are highlighted due to such advantages as free charging/discharging because a memory effect rarely occurs in the lithium secondary batteries when being compared with nickel-based secondary batteries, very low self-discharging rate, and high energy density.
The lithium secondary battery mainly uses lithium-based oxide and a carbon material respectively as a cathode active material and an anode active material. The lithium secondary battery includes an electrode assembly, in which a cathode plate and an anode plate, on which the cathode active material and the anode active material are respectively applied, are arranged as a separator is disposed between the cathode plate and the anode plate, and an exterior member, in which the electrode assembly is sealed and accommodated with an electrolyte, that is, a battery case.
Recently, secondary batteries have been widely used in a medium and/or large-scale device such as a vehicle and a power storage device, as well as a small device such as a portable electronic device. When a secondary battery is used in a medium and/or large-scale device, the secondary battery is provided as a battery pack, in which a plurality of battery cells that are electrically connected to one another are packaged, in order to increase a capacity and an output.
In the battery pack, a terminal is exposed outside in order to be connected to an external power supply after penetrating through the case. A battery pack according to the related art includes an additional sealing member such as a rubber packing member provided between a terminal and a terminal through unit, in order to prevent external moisture or impurities from being introduced into a case via the terminal through unit that is formed in the case so that the terminal may penetrate.
However, in the battery pack of the related art, in a case where the sealing member is corroded or is not exactly mounted, a gap easily generates and moisture or impurities may easily infiltrate into the case.
Also, the battery pack according to the related art has to include an additional sealing member for a waterproof function, and it increases manufacturing costs.
Thus, it is necessary to search for a method of providing a battery pack capable of achieving a waterproof function without using an additional sealing member.